The present invention is directed to a power drive for a sliding door and is particularly adapted for driving sliding doors employed on automotive van type vehicles.
Manually operable sliding doors have been utilized for many years on vans to provide a relatively large door opening at one side of the vehicle affording convenient access to the cargo 10 or rear passenger compartment of the van. Because this sliding door is universally located on that side of the vehicle remote from the drivers seat, and thus requires the driver to leave his seat to open or close the door, power drive systems operable by controls accessible from the drivers seat have been developed and are disclosed in the prior art. See, for example, U.S. Pat. Nos. to Shibuki et al., 4,462,185 and Schindehutte 4,644,692.
In the development of a power drive system for a sliding door employed on an automotive vehicle, certain factors peculiar to this particular application must be considered. First, the door is mechanically latched in its closed position by well known latch mechanisms and must be manually released by manually operable door handles located at the inner and outer sides of the door. Thus, powered opening of the door from its latched closed position necessarily requires a manual release of the latch before the door can move from its closed position. The latch releasing door handles are out of reach from the drivers seat.
Second, in many situations, it is more convenient to operate the door manually, and it is essential that the door be capable of being manually operated without interference from the power drive in the event of a malfunction or failure of the power drive system. Thus, the power drive system should provide the capability of accommodating a shifting from power to manual operation or vice versa with the door in any position on its path of travel.
Third, when the door is in its fully closed position, the outer surface of the door is flush with the outer surface of the vehicle body. The door is mounted upon the vehicle body for sliding movement by rollers carried by the door which are received in roller tracks fixedly mounted on the vehicle body. During initial movement of the door away from its closed position, the door must move outwardly away from the longitudinal centerline of the vehicle until the inner side of the door clears the outer side of the vehicle body. The door is then moved rearwardly past the outer side of the vehicle body along a path parallel to the vehicle centerline. This path is determined by the configuration of the tracks which support the door carried rollers and these tracks extend from their rearward ends forwardly parallel to the vehicle centerline and are then curved inwardly toward the centerline at their forward ends, these inwardly curved portions of the tracks establishing the inboard and outboard components of movement of the door to and from its closed position within the recessed door opening. A resilient door seal extending around the periphery of the door opening must be compressed by the door during the final phase of its movement to its fully closed position, this compressive force being applied in a direction normal to the vehicle centerline. Where the power drive arrangement is such that the powered force supplied to the door acts in a direction parallel to the vehicle centerline, the inboard inclination of the door carrying tracks referred to above reduces the effective force applied to the door at a time when the maximum application of force is required to compress the door seal. One approach to this problem is disclosed in the Schindehutte Patent 4,644,692 referred to above.
Another factor which must be considered is that the length of the path of movement of the door between its closed and open position is fairly substantial and the drive mechanism must include at least one component movable with the door over the entire length of the path of movement of the door. Exposure of moving parts of the drive should be minimized, and space within cavities or shielded recesses within the vehicle body for protectively enclosing components of the drive system is extremely restricted.
Finally, because in the usual case a power drive system for the sliding door will be marketed as a buyers' option, the system should be so designed that its installation requires no substantial alterations to a standard manually operable sliding door.
The present invention is directed to a power drive system for a sliding door which incorporates latch release mechanism automatically operable upon powered opening of the door from its closed position, a drive mechanism which accommodates unrestricted shifting between manual and powered operation at any door position and maintains direct alignment between the direction of positive drive powered force applied and the direction of movement of the door throughout the full range of door movement, which requires a minimum exposure of components of the drive system, and which may be assembled to operate a standard manually operable sliding door without requiring any substantial modification of the standard door or vehicle body.